geodiversity
The geopark region is a mountainous area carved by narrow valleys with a mean altitude varying between 200 and 600 m (at Freita and Montemuro Mountains the altitude reaches 1100-1200m). The geomorphology of the Arouca Geopark is strongly conditioned by hercynian tectonics responsible not only for the main foldings and mountain relieves but also for the main fault systems. The geopark is integrated in one of the major morphostructural units of the Iberian Peninsula: the Hesperian Massif, which is the largest fragment of the Variscan basement that crops out in Europe. The region is characterized, in general, by a low metamorphosed Palaezoic succession that rests unconformably over a Pre-Ordovician basement where thick siliciclastic formations of Ediacarian to Lower Cambrian age prevail. Variscan granitic bodies intruded into this Pre-Mesozoic sedimentary sequence also occur. Therefore, in the Arouca Geopark area three large geological groups are represented: the basement (metasedimentary rocks of the Schist-Greywacke Complex), the Palaeozoic sequence (Ordovician and Silurian quartzites and schists) and the magmatic bodies (sin-orogenic granitoids differentiated into six main plutonic bodies). Continental Carboniferous outcrops formed by clastic rocks that belong to an important regional formation are also registered. River and slope deposits, associated with the current hydrographic system, correspond to the modern sedimentary units of Quaternary age. One of the most distinctive characters of the geopark geodiversity is due to the high fossil content of the Ordovician slates, together with a peculiar phenomenon associated with a specific granitic body.